On Feb 3, 9:40*pm, "Edwin Pawlowski" wrote:
wrote in message
The
thermostat is about 20 years old.

Probably broke after 20 years. *Since you don't use all the features, buy a
cheap manual one and be warm.

Try removing the batteris for half an hour or follow the full reset
procedure in the manual, or see if there is a reset button you can
push with a pen, etc. If that doesn't work, then buy a new one.